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Author name code: krijger
ADS astronomy entries on 2022-09-14
author:"Krijger, J."
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Title: The New SCIAMACHY Reference Solar Spectral Irradiance and
Its Validation
Authors: Hilbig, T.; Weber, M.; Bramstedt, K.; Noël, S.; Burrows,
J. P.; Krijger, J. M.; Snel, R.; Meftah, M.; Damé, L.; Bekki, S.;
Bolsée, D.; Pereira, N.; Sluse, D.
2018SoPh..293..121H Altcode:
This paper describes a new reference solar spectrum retrieved from
measurements of the satellite instrument SCIAMACHY in the wavelength
region from 0.24 μ m to 2.4 μ m and its comparison with several
other established solar reference spectra. The SCIAMACHY reference
spectrum was recorded early in the mission before substantial optical
degradation due to the harsh space environment sets in. The radiometric
calibration of SCIAMACHY, applied in this study, includes a physical
model of the scanner unit. Furthermore, SCIAMACHY's internal white
light source (WLS) is used to correct for on-ground to in-flight
changes. The resultant calibrated solar spectrum from SCIAMACHY is
in good agreement with several available solar spectral irradiance
(SSI) references in the visible spectral range. Strong throughput
losses due to detector icing in the near infrared (NIR) are now
adequately accounted for. Nevertheless, a deficit with respect to the
ATLAS-3 composite and SORCE/SIM SSI is observed in the NIR. However,
the SCIAMACHY solar reference spectrum agrees well with the recently
re-evaluated SOLAR/SOLSPEC-ISS and recent ground measurements taken
at Mauna Loa in the NIR.
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Title: Improved Correction for Contamination-Induced In-Flight
Instrument Degradation of SCIAMACHY
Authors: Snel, R. C.; Krijger, J. M.
2015ESASP.735E..13S Altcode:
SCIAMACHY suffers from degradation due to contamination of the scan
mirror surfaces, optical components in the Optical Bench Module, and
detector surfaces.We have improved the polarisation and degradation
description of the instrument as well as the optical ground support
equipment used for initial on-ground instrument calibration. This
allows for a consistent model of the instrument for both on-ground
and in-flight conditions, and for arbitrary amounts of contamination
of the instrument.Using this model we have re-analysed the in-flight
calibration and monitoring data to arrive at an improved description
of the throughput and polarisation sensitivity of SCIAMACHY, for any
time during its mission.
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Title: The new SCIAMACHY calibration and degradation approach and
validation
Authors: Krijger, J. M. Matthijs; Snel, R.; Bovensmann, H.; Eichmann,
K. U.; Noel, S.; Liebing, P.; Richter, A.; Buchwitz, M.; von Savigny,
C.; Rozanov, A.; Bramstedt, K.; Gerilowski, K.; Vountas, M.; Burrows,
J. P.; van der Meer, P.; van Hees, R.; Aben, I.; Lichtenberg, G.;
Slijkhuis, S.; Doicu, A.; Schreier, F.; Hrechanyy, S.; Kretschel,
K.; Meringer, M.; Hess, M.; Gottwald, M.; Aberle, B.; Scherbakov,
D.; Gimeno-Garcia, S.; van Gijsel, J. A. E.; Tilstra, L. G.; Lerot,
C.; Van Roozendael, M.; Dehn Serco, A.; Fehr, T.
2010cosp...38..101K Altcode: 2010cosp...38..101M; 2010cosp.meet..101K
This presentation covers the highlights of the radiance, irradiance,
polarisation and degrada-tion re-characterisation of SCIAMACHY
and its validation. The imaging spectrometer SCIA-MACHY on ENVISAT
has been collecting data since launch in 2002. Over the years the
exposure to space has affected the optical performance and rendered the
on-ground calibra-tion data increasingly more outdated. As the overall
calibration quality is continuously being improved through better
in-flight characterisation and updated algorithms, instrument aspects
with previously acceptable errors are now in need of improvement. This
required re-analysis of the on-ground calibration measurements, and
pivots on measurements which were initially not intended for this
type of calibration and an improved mirror-model for the scanner
unit. Ad-ditionally, with the new approach it is possible to derive
scan-angle dependended degradation-corrected calibration key data for
the contaminated mirror surfaces in the scanner unit, thus improving
the radiometric, polarisation, and scan-angle calibration of the
instrument. We will present the new calibration approach and the first
results of the validation.
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Title: Observations of Umbral Flashes
Authors: Rouppe van der Voort, L. H. M.; Krijger, J. M.
2003csss...12..607R Altcode:
We present observations of oscillations in the chromosphere of the
umbra of sunspots. The observations were obtained with the Swedish
Vacuum Solar Telescope (SVST) and the Dutch Open Telescope (DOT)
on La Palma, comprising spectrograms and filtergrams in the Ca II H
line. The sawtooth pattern in the spectroscopic time evolution of the Ca
II H core is shown as well as evidence for a connection between umbral
flashes and running penumbral waves from image sequences. Running waves,
coherent over a large fraction of the penumbra, seem to be excited by
flashes that occur close to the umbra-penumbral boundary. Comparing
the intensity oscillations in the Ca II H line with TRACE observations
in the 1600 Å passband, we find a phase difference of approximately
25 ° with 1600 Å leading the Ca II H intensity oscillation which we
attribute to complex dynamical behaviour.
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Title: Dynamics of the solar chromosphere IV. Evidence for atmospheric
gravity waves from TRACE
Authors: Rutten, R. J.; Krijger, J. M.
2003A&A...407..735R Altcode:
We study the low-frequency brightness modulation of internetwork
regions in the low solar chromosphere using simultaneous ultraviolet
and white-light image sequences from the Transition Region and Coronal
Explorer (TRACE). The ultraviolet sequences exhibit a slowly varying
brightness pattern in internetwork regions on which the more familiar
acoustic three-minute oscillation is superimposed, with about half of
the peak brightness reached in internetwork grains contributed by the
low-frequency background. We address the nature of the latter, applying
two-dimensional Fourier filtering to isolate it from the acoustic
modulation. Spatio-temporal comparisons and selective time-delay scatter
correlations between the ultraviolet and white-light low-frequency
sequences establish that reversed granulation constitutes at most a
minor part of the ultraviolet background. Fourier analysis shows that
the meso-scale contribution dominates and consists of atmospheric
gravity waves.
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Title: La Palma observations of umbral flashes
Authors: Rouppe van der Voort, L. H. M.; Rutten, R. J.; Sütterlin,
P.; Sloover, P. J.; Krijger, J. M.
2003A&A...403..277R Altcode:
We present high-quality Ca II H & K data showing chromospheric
flashes in sunspot umbrae collected with the Swedish Vacuum Solar
Telescope, the Dutch Open Telescope, and the Swedish 1-m Solar Telescope
at the Roque de los Muchachos Observatory on La Palma. Differential
movies, time slices, spectrograms, and Fourier power maps demonstrate
that umbral flashes and running penumbral waves are closely related
oscillatory phenomena, combining upward shock propagation with coherent
wave spreading over the entire spot. We attribute the flash brightening
to large redshift by post-shock material higher up. We find no obvious
relation between umbral dots and umbral flashes.
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Title: Photospheric flows measured with TRACE II. Network formation
Authors: Krijger, J. M.; Roudier, T.
2003A&A...403..715K Altcode:
We analyse a 7 d (167 h) sequence of TRACE white-light images with 1
arcsec angular resolution taken at 1 min cadence. The TRACE resolution
and the fast cadence allows us to produce maps of the horizontal
flow fields with high angular (1 arcsec) and temporal resolution (5
min). The field of view of 128arcsec x 128arcsec (~93 Mm x 93 Mm)
covers approximately an area of 10 to 30 supergranules. This area
was followed during solar rotation. Magnetic flux was artificially
inserted into the successive flow maps in the form of ephemeral
regions with positive and negative polarity. The emergence rate of 2
x 10<SUP>22</SUP> Mx h<SUP>-1</SUP> with an average flux per region
of about 1.1 x 10<SUP>19</SUP> Mx produces a good reproduction of the
chromospheric network as observed in images taken simultaneously at
1600 Å. In addition, we show that the quiet network can be maintained
only if field elements of both polarities are inserted into the flow
fields. Our analysis suggests that the network is fully replenished
on a time scale of a day and the lifetimes of the magnetic elements
are of a similar duration.
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Title: Verification of SCIAMACHY's Polarisation Correction over the
Sahara Desert
Authors: Tilstra, L. G.; Acarreta, J. R.; Krijger, J. M.; Stammes, P.
2003ESASP.531E..13T Altcode:
No abstract at ADS
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Title: Current Status of SCIAMACHY Polarisation Measurements
Authors: Krijger, J. M.; Stammes, P.
2003ESASP.531E..14K Altcode:
No abstract at ADS
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Title: The "careers in solar physics" session of the SPM10 meeting
Authors: Aulanier, G.; Parenti, S.; Krijger, J. M.
2002ESASP.506..981A Altcode: 2002ESPM...10..981A; 2002svco.conf..981A
During the SPM10 meeting held in Prague (Czech Republic) on September
9-14, 2002, a half-day 'young session' was organized on the topic
of careers in solar physics. Several young researchers and senior
scientists were invited to give oral contributions on the current
advantages and difficulties attached to the current system for
post-doctoral contracts. A scientist from USA also presented the
American system for contractors, and an ESA representative presented
the official position of ESA regarding funding researchers. From
the talks as well as from the long open discussion which followed,
it was widely agreed that several typical rules for EU post-doc
contracts (their short duration, their mandatory mobility, their
age limit and their administrative and financial difficulties) not
only lead to serious problems in the private life of postdocs, but
essentially can have serious drawbacks on the follow-up of long-term
scientific developments, and could quickly result in a dramatic loss
of expertise, from the scale of individual institutes to the European
scientific community at large. Many participants and most of the young
researchers naturally agreed that new longer-term, renewable and stable
contracts are necessary. In order to create such types of contracts,
several fund raising initiative achieveable by the scientific community
were discussed. The development of better public outreach initiatives
on the European scale was a possibility which federated most of the
participants. The resulting conclusion on this session were transmitted
to the new board of the Solar Physics Section of the EAS/SPS.
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Title: Origin and evolution of ices around massive young stars
Authors: Krijger, Johannes Mattheus
2002PhDT.......215K Altcode:
The thesis Structure and dynamics of the solar chromosphere of
J.M. Krijger is a study on the behavior of the solar chromosphere,
the thin layer just above the solar surface (photosphere) visible
in purple red light during a total solar eclipse. The most important
result of this thesis is that the chromosphere is filled with acoustic
and internal gravity waves that travel upward until they collide
with a canopy of expanding magnetic field. The photosphere is the
layer of which we see the light with the naked eye. Through this
layer poke large and small magnetic tubes. Above the photosphere
and the chromosphere sits the hot solar corona of a few million
degrees. With observations of among others the space satellite TRACE
(Transition Region and Coronal Explorer) J.M. Krijger shows that the
photosphere is dominated by flows of the ambient gas that dictate the
magnetic field where to go. The possible heating of the chromosphere
is an important unsolved problem in solar physics. The chromosphere
forms the transition region between the very hot corona, dominated by
magnetic fields, and the photosphere where gasflows drag the magnetic
field along. In this transition region the magnetic field, which in the
photosphere is still trapped in individual tubes, expands to a canopy
above which the magnetic field fills the entire space. In this thesis
it is shown that the chromosphere is dominated by upward propagating
acoustic waves and a magnetic canopy that changes the dynamics of the
oscillations. Finally J.M. Krijger shows that the network of magnetic
field in the chromosphere is formed by magnetic tubes that are swepped
together by flows in the photosphere.
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Title: Photospheric flows measured with TRACE
Authors: Krijger, J. M.; Roudier, T.; Rieutord, M.
2002A&A...387..672K Altcode:
We analyse white-light image sequences taken with the Transition
Region and Coronal Explorer (TRACE) using an optimised local
correlation tracking (LCT) method to measure the horizontal flows
in the quiet solar photosphere with high spatial (1 arcsec) and
temporal (5 min) resolution. Simultaneously taken near-ultraviolet
images from TRACE confirm that our LCT-determined flows recover the
actual supergranulation pattern, thus proving that the topology of the
horizontal flow distribution and network assembly may be studied from
long-duration TRACE white-light sequences with our method.
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Title: Structure and dynamics of the solar chromosphere
Authors: Krijger, Johannes Mattheus Thijs
2002PhDT.......228K Altcode:
No abstract at ADS
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Title: Dynamics of the solar chromosphere. III. Ultraviolet brightness
oscillations from TRACE
Authors: Krijger, J. M.; Rutten, R. J.; Lites, B. W.; Straus, Th.;
Shine, R. A.; Tarbell, T. D.
2001A&A...379.1052K Altcode:
We analyze oscillations in the solar atmosphere using image sequences
from the Transition Region and Coronal Explorer (TRACE) in three
ultraviolet passbands which sample the upper solar photosphere and
low chromosphere. We exploit the absence of atmospheric seeing in
TRACE data to furnish comprehensive Fourier diagnostics (amplitude
maps, phase-difference spectra, spatio-temporal decomposition) for
quiet-Sun network and internetwork areas with excellent sampling
statistics. Comparison displays from the ground-based Ca Ii H
spectrometry that was numerically reproduced by Carlsson &
Stein are added to link our results to the acoustic shock dynamics
in this simulation. The TRACE image sequences confirm the dichotomy
in oscillatory behaviour between network and internetwork and show
upward propagation above the cutoff frequency, the onset of acoustic
shock formation in the upper photosphere, phase-difference contrast
between pseudo-mode ridges and the interridge background, enhanced
three-minute modulation aureoles around network patches, a persistent
low-intensity background pattern largely made up of internal gravity
waves, ubiquitous magnetic flashers, and low-lying magnetic canopies
with much low-frequency modulation. The spatio-temporal occurrence
pattern of internetwork grains is found to be dominated by acoustic
and gravity wave interference. We find no sign of the high-frequency
sound waves that have been proposed to heat the quiet chromosphere, but
such measurement is hampered by non-simultaneous imaging in different
passbands. We also find no signature of particular low-frequency
fluxtube waves that have been proposed to heat the network. However,
internal gravity waves may play a role in their excitation.
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Title: Phase Relations between Chromospheric and Transition Region
Oscillations
Authors: Krijger, J. M.; Curdt, W.; Heinzel, P.; Schmidt, W.
2000ESASP.463..353K Altcode: 2000sctc.proc..353K
No abstract at ADS
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Title: COMPTEL detection of pulsed gamma -ray emission from PSR
B1509-58 up to at least 10 MeV
Authors: Kuiper, L.; Hermsen, W.; Krijger, J. M.; Bennett, K.;
Carramiñana, A.; Schönfelder, V.; Bailes, M.; Manchester, R. N.
1999A&A...351..119K Altcode: 1999astro.ph..3474K
We report on the first firm detection of pulsed gamma -ray emission
from PSR B1509-58 in the 0.75-30 MeV energy range in CGRO COMPTEL data
collected over more than 6 years. The modulation significance in the
0.75-30 MeV pulse-phase distribution is 5.4sigma and the lightcurve
is similar to the lightcurves found earlier between 0.7 and 700 keV:
a single broad asymmetric pulse reaching its maximum 0.38 +/- 0.03 in
phase after the radio peak, compared to the offset of 0.30 found in
the CGRO BATSE soft gamma-ray data, and 0.27 +/- 0.01 for RXTE (2-16
keV), compatible with ASCA (0.7-2.2 keV). Analysis in narrower energy
windows shows that the single broad pulse is significantly detected
up to ~ 10 MeV. Above 10 MeV we do detect marginally significant
(2.1sigma ) modulation with an indication for the broad pulse. However,
imaging analysis shows the presence of a strong 5.6sigma source at
the position of the pulsar. To investigate this further, we have also
analysed contemporaneous CGRO EGRET data (>30 MeV) collected over
a nearly 4 year period. In the 30-100 MeV energy window, adjacent
to the COMPTEL 10-30 MeV range, a 4.4sigma source can be attributed
to PSR B1509-58. Timing analysis in this energy window yields an
insignificant signal of 1.1sigma , but with a shape somewhat similar to
that of the COMPTEL 10-30 MeV lightcurve. Combining the two pulse-phase
distributions results in a suggestive double-peaked pulsed signal above
the background level estimated in the spatial analyses, with one broad
peak near phase 0.38 (aligned with the pulse observed at lower energies)
and a second narrower peak near phase 0.85, which is absent for energies
below 10 MeV. The modulation significance is, however, only 2.3sigma
and needs confirmation. Spectral analysis based on the excess counts in
the broad pulse of the lightcurve shows that extrapolation of the OSSE
power-law spectral fit with index -1.68 describes our data well up to
10 MeV. Above 10 MeV the spectrum breaks abruptly. The precise location
of the break/bend between 10 and 30 MeV depends on the interpretation
of the structure in the lightcurve measured by COMPTEL and EGRET above
10 MeV. Such a break in the spectrum of PSR B1509-58 has recently been
interpreted in the framework of polar cap models for the explanation of
gamma-ray pulsars, as a signature of the exotic photon splitting process
in the strong magnetic field of PSR B1509-58. For that interpretation
our new spectrum constrains the co-latitude to ~ 2degr , close to the
“classical” radius of the polar cap. In the case of an outer-gap
scenario, our spectrum requires a dominant synchrotron component.
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Title: Dynamics Of The Internetwork Chromosphere With TRACE
Authors: Krijger, J. M.
1999ESASP.446..391K Altcode: 1999soho....8..391K
The UV passbands of the Transition Region and Coronal Explorer
(TRACE; 170 nm, 160 nm, 155 nm, respectively) sample the low
chromosphere. Quiet-sun regions display brightness patterning much like
Ca II H &K, including internetwork grains akin to the so-called K2v
grains. We demonstrate this pattern correspondence with simultaneous
TRACE and La Palma data, study and we Fourier-analyze high-cadence
TRACE image sequences to obtain power, coherence and phase difference
spectra, separately for network and internetwork.
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Title: COMPTEL Detection of Pulsed Emission from PSR B1509-58 up to
at Least 10 Mev
Authors: Kuiper, L.; Hermsen, W.; Krijger, J. M.; Bennett, K.;
Schönfelder, V.; Carramiñana, A.; Manchester, R.; Bailes, M.
1999ApL&C..38...33K Altcode: 1998astro.ph.12405K
We report the COMPTEL detection of pulsed $\gamma$-emission from PSR
B1509-58 up to at least 10 MeV using data collected over more than 6
years. The 0.75-10 MeV lightcurve is broad and reaches its maximum near
radio-phase 0.38, slightly beyond the maximum found at hard X-rays/
soft $\gamma$-rays. In the 10-30 MeV energy range a strong source is
present in the skymap positionally consistent with the pulsar, but we
do not detect significant pulsed emission. However, the lightcurve is
consistent with the pulse shape changing from a single broad pulse
into a double-peak morphology. Our results significantly constrain
pulsar modelling.